There has been described in the past numerous methods and materials for use in determining the presence of biological substances in a sample under analysis, particularly antigens and antibodies, and particularly when that sample is a human body fluid. One of the most commonly employed methods is an enzyme linked immunoabsorbent assay (ELISA). ELISA-type assays are often performed with the use of microtiter plates, which may be generally described as a plate molded out of a plastic or a similar material, having numerous wells for receiving aliquots of a sample and assay reagents. Microtiter plates are commonly employed in a clinical setting for the assaying of physiological fluid or excreta for the presence of a target analyte, which may often be an antibody or antigen. In fact, microtiter plates may even in some cases be purchased with antibodies already added to the wells, specific for the particular antigen under investigation. In preparing such pre-coated microtiter plates, individual aliquots of the antibody are either manually pipetted into each well to coat its bottom, or added to a series of the wells through automated pipetting techniques. Once in the laboratory setting, an aliquot of a sample under analysis is added to each well of the microtiter plate, usually by use of manual pipetting techniques. The sample is then allowed to interact with the antibody.
Frequently the number of individual wells in these microtiter plates can be very large. Repetitive pipetting, whether automated or manual leaves a large margin for error in the uniformity of coating of the antibody aliquots into each individual well. Non-uniformity of coating can introduce variability to the assay results, diminishing reliability of the assay and also affecting the overall sensitivity of the test.
Also, determinations utilizing ELISA-type technique generally demand a large amount of reagents which are oftentimes limited in supply because they are difficult or costly to obtain. Furthermore, the reaction time period necessary to carry out these types of assays practiced in the art, generally ranges about 2-4 hours.